Japanese Patent Laid-Open No. 10-253871 discloses a focus detection apparatus as a conventional method of adjusting and fixing an image sensing element. The arrangement of this apparatus is shown in FIG. 18. The apparatus has a light-receiving element 111 on which an object image is projected via an imaging lens 110, and a sensor holding member 112 which holds the light-receiving element 111. By rotating and moving the light-receiving element 111 on the sensor holding member 112, the inclination around the optical axis (along the first axis) can be adjusted. By translating the light-receiving element 111 on the sensor holding member 112, shifts along second and third axes perpendicular to each other on a plane almost perpendicular to the optical axis of the imaging lens 110 can be adjusted.
The sensor holding member 112 is equipped with adjusters 113 which are able to move in parallel with the first axis and have hinges 113a for rotatably attaching the adjusters 113 to the sensor holding member 112. Each adjuster 113 is reciprocally attached to a holder 114 so as to be almost parallel to the first axis. Notches 112a are brought into contact with the hinges 113a to rotatably attach the sensor holding member 112, and an inclination around the second axis can be adjusted in the light-receiving element 111. At least one of the adjusters 113 is reciprocated along the optical axis, and the light-receiving element 111 can adjust an inclination around the third axis. In addition, the adjusters 113 are reciprocated with respect to the holder 114 by almost the same amount, and a shift along the first axis can be adjusted. This realizes adjustment of a total of six axes, i.e., along and around the first, second, and third axes.
After adjustment of the six axes is performed by the above mechanism, the light-receiving element 111 and sensor holding member 112, the sensor holding member 112 and adjusters 113, and the adjusters 113 and holder 114 are adhered to each other. As a result, the light-receiving element 111 is fixed to the holder 114.
The conventional method adopts an arrangement in which even a temperature change of a building member hardly causes a positional change of the light-receiving element 111. To cope with this, the optical member itself must hardly change in position. However, if the imaging lens 110 is made of a plastic in the conventional arrangement, a temperature change causes a positional shift due to a large linear expansion coefficient (see Table 1).
TABLE 1LinearFlexuralExpansionElasticCoefficientModulusPart NameMaterial(× 105 mm/° C.)(× 104 N/mm)SupportPlastic1.5002.43MemberImage SensingMetal0.2607.00ElementCover GlassGlass0.3788.60PhotographingPlastic7.0000.24LensCap GlassGlass0.8107.15AdjustmentMetal0.86011.00MemberSilicon-BasedResin5.0000.0002AdhesiveInstantCyanoacrylate13.0000.0421Adhesive
To prevent this, glass is used to decrease the linear expansion coefficient of the imaging lens 110, satisfying the performance. However, the glass is expensive, so the performance must be satisfied using a plastic lens for cost reduction of the apparatus.